On Sat, 16 Jul 2016 03:58 pm, Rustom Mody wrote: > > From other thread: > > On Saturday, July 16, 2016 at 9:50:13 AM UTC+5:30, Ethan Furman wrote: >> On 07/15/2016 09:04 PM, Rustom Mody wrote: >> >> > Just that suggesting that python's bool notion is straightforward is an >> > unnecessary lie – especially to newbies. >> >> Python's boolean concept is as simple as it gets -- what is not >> straightforward about it? > > And to expand on my > > On Saturday, July 16, 2016 at 11:18:48 AM UTC+5:30, Rustom Mody wrote: >> FWIW My belief: In general its nonsensical > > C's 0 is false; rest-of-universe is true is a mess
Really? In what way? As far as I know, C requires bools to be ints, not arbitrary values, and the compiler will enforce that. What mess do you get from C allowing 2 as well as 1 to be treated as true? > Python increases the mess by making the false-y candidates also > non-singleton So you say, but you haven't demonstrated this. > This seems to work for container-like objects like lists,strings,sets, etc > with None and 0 being somewhat elliptical analogues Right. This is a good, concrete, practical example that duck-typed truthy and falsey values DOES work: it works for numbers, it works for strings, it works for containers. > But when we allow __bool__ to be available for any and every thing and > give it some implicit random definition, this is just plain nonsense. > > [What is the bool-nature -- aka Buddha-nature -- of graphs question > [remains yet answered] No, I already answered that in the earlier thread. Graphs are collections or sequences of nodes. An empty graph (one with zero nodes) should be falsey; all other graphs (one or more nodes) should be truthy. I say "should", not "must". Practicality beats purity: if your application has a specific need for (let's say) a graph with exactly two cycles to be considered falsey, and all others to be truthy, then you are free to define your graph type that way. As an internal application-only class, that's probably okay, but as a generic graph type in a library, it's probably a bad idea. -- Steven “Cheer up,” they said, “things could be worse.” So I cheered up, and sure enough, things got worse. -- https://mail.python.org/mailman/listinfo/python-list
